What would cause a front tranny seal to blow?

How hot was the tranny when you were making your pass? The reason why I ask is because my car did the same thing a couple of months ago when the tranny would get too hot. It would puke tranny fluid all over the road and smoke like a train. It was coming from the bellhousing area too. Once it cooled off it wouldn't leak a drop. I was running a trans cooler that was too small for my convertor. Swapped to a bigger trans cooler and never happened again. Hope this helps. Has it leaked since cooling off?

Oh yeah everyone was saying a cracked convertor with my problem too.